Communication devices of various kinds rely on various circuitries to control different aspects of electronic communication between devices. With the rise of wireless communication devices such as mobile phones, smart phones, tablet computers, and other mobile devices that communicate wirelessly, power and battery efficiency have become a significant concern.
An example circuit schematic for a typical wireless receiver is illustrated in FIG. 1. An input 105 is configured to receive signals at an integrated circuit (IC) from an antenna 110 disposed on a printed circuit board (PCB). The input signal travels through a low noise amplifier core 134 and center-tapped transformer 136 to a mixer circuit 140. The mixer circuit 140 provides an output to baseband filters 160 (BBF) for blocker rejection, which provide filtered signals to analog to digital conversion circuits 165 that convert the analog output from the receiving circuitry to a digital signal for use by the receiving device associated with the antenna 110.
One way to conserve power in a wireless radio is to power down the circuitry of the radio (typically in what is called a low power mode) when the radio is not being used. A problem with this approach is that the radio needs to be a least periodically powered up to detect whether another device is trying to send a communication to the radio. However, this takes a long time to wake-up, thereby reducing battery longevity.
One approach to solving this problem is to include a separate lower power radio for detecting the incoming signal. This approach, however, requires more hardware built into the communication device, increasing the die area and the cost. Another approach is to configure the radio of the communication device to listen for the incoming communication, which approach costs more current and battery life. Moreover, with the increasing abilities of modern communication devices, there is pressure to have the radio wake-up process occur in a very fast wake-up time with low latency while also conserving battery life. At the same time, the wake up receiver shall maximally use the hardware already allocated for the main receiver.